(1) Method of Setting a Range for Precise Examination in CT (Computed Tomography) Examination
In a CT examination, a scanogram is taken first, and slice positions and a range are subsequently determined based on the scanogram before taking CT images. Next, screening (assessment of the presence or absence of a lesion) is performed using the CT images to perform a precise examination. Hereinbelow, the term “precise examination” refers to an examination that is performed in a CT examination with the purpose of observing a lesion when the presence of a lesion is suspected based on the results of screening.
When performing a precise examination, imaging conditions are set to obtain more detailed and clearer CT images than images obtained by screening, and then CT images are taken again. In an example of examining lung, images are taken for screening by employing a slice thickness of 10 mm and a table speed of 10 mm, while in a precise examination images of only a region where existence of lesion is suspected in the screening are produced again by employing a slice thickness of 2 mm and a table speed of 2 mm.
Although in screening an imaging range is generally set to cover all the organs, in a precise examination only a region where existence of a lesion is suspected is usually set as an object of imaging. This is because taking an image again in a precise examination of a region where a lesion is not observed in screening would constitute unnecessary radiation exposure. Accordingly, the range of imaging in a precise examination is determined on the basis of the slice position of the CT images obtained by screening.
When setting the scanning conditions for a conventional precise examination, based on the results of observation of CT images obtained in screening (FIGS. 11(1) and 11(2)), the operator transcribes the slice positions of the CT images where existence of a lesion is suspected into a memo pad (FIG. 11(3)) (depending on the sizes or number of lesions, a plurality of slice positions may be transcribed). Then, as shown in FIG. 12, the operator sets the slice positions while looking at the slice positions written in the memo pad. Since the slice positions are written with 5 digits or more, such as 1234.5 mm, it is difficult to remember the slice position mentally, and therefore many operators transcribe the positions into a memo pad.
Most current X-ray CT apparatuses employ a GUI (Graphical User Interface). Therefore, when observing images many operators hold a “mouse” in their dominant hand (the right hand in many cases). However, in order to transcribe a slice position into a memo pad, the operator must release the mouse from their dominant hand to hold a pen and write down the slice position in the memo pad. Then, when observing the screening images again, the operator must put down the pen and hold the mouse again. Thus, there is a problem that in order to record a range for a precise examination in a memo pad, an operator must switch holding a mouse over to holding a pen several times.
Further, in screening, a mistake may occur when a operator transcribes a slice position of CT image where existence of a lesion is suspected into a memo pad. There is also a possibility of a mistake occurring when setting slice positions for a precise examination based on the figures written into the memo pad.
Furthermore, in the conventional method using a memo pad, due to the complexity of the operations, a substantial time is required to set the scan conditions for changing from screening to precise examination. During the time period taken to change from screening to precise examination, the subject to be examined is not allowed to move from the table to avoid inconformity of slice positions between screening and precise examination, whereby the time for setting the scan conditions of the precise examination is weariness for the subject.
(2) Method of Setting a Slice Position for Rescanning in CT Examination
When an artifact appears in a specific CT image owing to a certain cause, such as movement of the subject, in a conventional technique, the operator first records the slice position of the CT image in which the artifact appears in a memo pad. Thereafter, the operator sets the slice position to be re-scanned while looking at the slice position written in the memo pad. In a similar manner to the above method (1), the operator must switch holding a mouse over to holding a pen several times in order to record the slice position to be re-scanned in the memo pad. There is a problem that recording these slice positions in a memo pad during the examination that requires speed is troublesome and complicated.
There also is a possibility that a mistake will be made when transcribing the positions of re-scanning in a memo pad or when setting the positions for rescanning based on the transcribed positions. Furthermore, for the same reasons as in the above (1), the operations involved in setting the slice positions of re-scanning require a lengthy time period and make the subject wearied.
(3) Method for Marking an Image to be an Important Factor in Diagnosis and a Method for Displaying the Image with the Marker in CRT Diagnosis
The term “CRT diagnosis” refers to displaying an image on a CRT (Cathode Ray Tube) to perform diagnosis without developing the image on film. In CRT diagnosis, an observer adds remarks to several CT images having clincher for diagnosis among a series of images, and stores the images and remarks as electronic data. When adding the remarks, text data are used as a means of adding character information, and ROI (Region of Interest), distance measurement, angle measurement, straight lines, curved lines, arrows and the like are used as a means for adding graphical information.
When the stored electronic data of the stored series of images and remarks are read out again, CT images to which no remark is attached are displayed as they are, and CT images to which the remark is attached are displayed together with the character information and/or graphical information.
Attaching the text data, ROI, distance measurement, angle measurement, straight line, curved line, arrow or the like to the CT image, suffice it to say that play the role of “adding a marker (remark) to a CT image”. However, while the function that adds these kinds of character information and graphical information is to indicate and measure a lesion visualized in a CT image, it is not a function of indicating the CT image of diagnostic importance itself.
In CRT diagnosis, there are cases where it is more appropriate that an observer adds neither character information nor graphical information to a lesion visualized on several CT images having diagnostic clincher among a series of CT images. For example, when observing a state that a tumor is stained by a contrast medium according; to a lapse of time, or when observing a state where a tumor is gradually becoming small as a result of periodic observation or the like, observation is facilitated when superfluous characters or graphics are not displayed on the CT image.
In this case, rather than adding a marker to the lesion on the CT image, it is more appropriate to add a marker to the CT images of diagnostic importance. However, that type of method has not existed up to now. Therefore, when observing a state that a tumor is stained by a contrast medium according to a lapse of time in the conventional method, the observer observes CT images that are seemingly considered to be of the same slice position, whereby there is a problem that the method lacks certitude. Furthermore, when stored electronic data for a series of images and remarks are read out again, CT images to which the remark is not attached are displayed as they are, and CT images to which the remark is attached are displayed together with the character information and/or graphical information.
When adding a marker to a CT image in the conventional method, text data, ROI, distance measurement, angle measurement, straight line, curved line, arrow or the like is used as the marker. Because keyboard operation or mouse operation involving several steps is respectively required to add the marker, these are not suitable for the purpose of adding the marker to the CT image itself.
Furthermore, when a series of image data is readout that includes a CT image to which a remark was added, in order to display the CT image having the remark out of the plurality of images, it is necessary for an operator to check images one by one starting from the first image to locate the image with the remark in it. It has thus been necessary to carry out image update operations several times until the CT image with the remark in it is displayed. Furthermore, when there is a plurality of CT images of diagnostic importance, there has been a drawback that a position where the images with the remark in it (images of diagnostic importance) is unknown until all the images are displayed at once.
(4) Method of Adding Markers to Images of Diagnostic Importance and Filming the Images (Printing the Images on Photographic Film) in CT Examination
In a similar manner to CRT diagnosis, in diagnosis using film an observer adds remarks to several CT images having clincher in diagnosis out of a series of film. When viewing the film to diagnose, particular attention is paid to CT images to which the observer has added remarks among the series of CT images.
In a conventional technique, in the same manner as in the CRT diagnosis of the above (3), text data, ROI, distance measurement, angle measurement, straight line, curved line, arrow or the like is also added to the CT images for filming.
In a conventional technique, no method of adding a marker to the CT image having diagnostic clincher exists other than adding a remark to a CT image on film.
Further, in the conventional technique, when explaining a treatment area or an examination area to a subject, because the difference between abnormality and normality is not known by the average subject, it has been necessary for a physician to write directly on a frame of film or to attach a piece of paper or the like. However, it is not preferable from the viewpoint of maintaining the medical information to afterward process the film.
With respect to filming, as in the above (3), when adding a marker to a CT image, text data, ROI, distance measurement, angle measurement, straight line, curved line, arrow or the like is used as the marker as in the above (3) since keyboard operations or mouse operations involving several steps are respectively required for each type of the marker, these types are not suitable for the purpose of adding a marker to a CT image itself.
The present invention is provided in view of the foregoing, and it is an object of the invention to provide a method for displaying images and a method for performing radiography of image that make it possible to accurately set of a range for precise examination and slice positions for rescanning in a short time by a simple operation.
Another object of the present invention is to provide a method for displaying images that easily displays a tomogram of an important factor for diagnosis certainly at the same tomographic position, or for filming as such.